An exterminator named Jason Smith was arrested and charged today in the strangling and burning death of Philadelphia pediatrician Melissa Ketunuti.

Smith, 36, had been sent to Ketunuti's home on a service call where the two got into "some kind of argument" in Ketunuti's basement on Monday, Capt. James Clark of the Philadelphia police department said this morning.

"At her home they got into an argument. It went terribly wrong. He struck her, and knocked her to the ground," Clark said. "Immediately he jumped on top of her, started strangling her. She passed out, and then he set her body on fire."

Clark said Smith burned the woman's body "to hide evidence like DNA." He said "at some point, he bound her up." The doctor was found with her hands and feet tied behind her back.

The captain said that before today's arrest Smith's record consisted of only "minor traffic offenses."

Police received a call from Ketunuti's dog-walker about the house fire around 12:30 p.m. Monday, and once inside found Ketunuti with her hands and feet bound. They believe Smith hit her and strangled her with a rope, causing her to pass out, and then bound her body and set fire to it in order to destroy evidence, including DNA evidence.

Ketunuti, 35, was fully clothed and police do not believe she was sexually assaulted.

She was a doctor at Children's Hospital of Philadelphia and had lived alone in the Graduate Hospital neighborhood of the city for about three years.

Clark said that homicide detectives scoured the neighborhood for surveillance videos from nearby stores and businesses, and through the video identified the suspect.

Smith was spotted on video getting out of the vehicle and following Ketunuti to her home. The man left her home after an hour and was seen on video circling her home.

Detectives drove to Clark's home in Levittown, Pa., outside of Philadelphia where he lives with a girlfriend and her child, on Wednesday night and brought him back to the Philadelphia police station.

A silver Ford truck was towed from Smith's home, which was the same truck spotted on surveillance video Monday in Ketunuti's neighborhood, sources told ABC News affiliate WPVI.

There, he gave statements that led police to charge him with the murders, Clark said.

Smith will face charges of murder, arson, and abuse of a corpse.

Ketunuti's hospital issued a statement Tuesday that she was "a warm, caring, earnest, bright young woman with her whole future ahead of her," adding that she will be deeply missed.